Metropolitan Climate Dashboard

Urban Heat Island

Building density 55%

Green cover 25%

Time of day 14:00

City core temp

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Rural temp

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Heat island Δ

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Avg albedo

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How it works

Every surface in the grid absorbs solar radiation according to its albedo, then re-radiates and convects that energy away. Dark asphalt and dense building mass absorb more sunlight and store it in a large thermal mass, so they release heat slowly through the night. Grass and tree canopy reflect more light, evaporate moisture (evapotranspiration) and hold almost no thermal mass, so they track the outside air closely. Packing buildings tighter also traps re-radiated heat between walls and blocks the sky view that lets heat escape at night — this is the urban canyon effect.

T(t+dt) = T + dt · [ α·I(t)·(1-shade) − k·(T−T_air) ] / C
I(t) = I_max · max(0, sin(π·(hour−6)/12))

Building density — fraction of the grid covered by buildings; higher density raises average albedo-weighted absorption and thermal mass, and traps more re-radiated heat between structures.
Green cover — fraction of non-built area given to grass/trees instead of bare asphalt; green cover reflects more light and cools evaporatively, pulling the local temperature toward the rural baseline.
Time of day — drives the solar irradiance curve; the heat island effect is usually largest a few hours after sunset, when the city's stored heat is still radiating out but the rural area has already cooled.
Day cycle — toggle automatic time advance to watch a full 24-hour cycle, or pause and scrub the time slider by hand.

Real-world relevance: this is exactly why city centers can be 3–7°C warmer than surrounding farmland on a calm summer night — a documented driver of higher cooling-energy demand and heat-related health risk that urban planners try to offset with reflective roofing and tree cover.

Hot surface Cool surface Green cover

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